Aquaporins (AQPs) are membrane water channels expressed in many mammalian tissues that carry out fluid transport. This competitive renewal builds on our discoveries of three novel, unanticipated AQP functions - cell migration, cell proliferation and neuroexcitation - each with the potential to yield new therapies for human diseases. The proposed studies utilize cell and mouse models of AQP gene deletion, knockdown and overexpression, and state-of-the-art biophysical methods. Aim 1 will elucidate cellular mechanisms of AQP-facilitated cell migration. Biophysical studies will be done to test the hypothesis that AQP expression in membrane protrusions in migrating cells facilitates water influx and lamellipodial dynamics. Aim 2 will elucidate cellular mechanisms of AQP3-facilitated cell proliferation. The hypothesis will be tested that AQP3-faciliated glycerol transport alters cellular glycerol metabolism, which is a key determinant of cellular ATP/energetics, MAPK signaling and biosynthesis. Aim 3 will elucidate the cellular mechanisms by which AQP4 facilitates the neurotransmission function of electrically excitable cells. Biophysical methods, including novel K+-sensitive fluorescent indicators developed by our lab, will be used to test our working hypothesis that AQP4 expression facilitates K+ reuptake by glial cells following neuroexcitation by an indirect osmotic mechanism involving solute-solvent coupling. In addition to establishing new paradigms on the physiological functions of AQPs, the proposed research will provide a rational basis for identification of AQP modulators for tumor therapy, accelerating wound repair, and medical management of epilepsy. PUBLIC HEALTH RELEVANCE: The aquaporins are a family of membrane transporters of water and glycerol. This proposal will establish cellular mechanisms by which aquaporins are involved in cell migration, cell proliferation and neuroexcitation. The outcomes of this research will include improved understanding and potential new therapies for tumors, wound healing and epilepsy.